“ push button, send product ” - Configuration, Version, and Release Management Sommerville, Chapter 29 Instructor: Peter Baumann email: p.baumann@jacobs-university.de tel: -3178 "Good, Fast, Cheap: office: room 88, Research 1 Pick any two (you can't have all three). " -- from RFC 1925 320312 Software Engineering (P. Baumann)
Symptoms of the Change Chaos Problems of identification and tracking: Problems of version selection: • “This program worked yesterday. • “Has everything been compiled? What happened?” Tested?” • “I fixed this error last week. • “How do I configure for test, Why is it back?” with my updates and no others?” • “Where are all my changes • “How do I exclude this from last week?” incomplete/faulty change?” • “This seems like an obvious fix. • “I can’t reproduce the error Has it been tried before?” in this copy!” • “Who is responsible for this change?” • “Exactly which fixes went into this configuration?” • “Oh shoot. I need to merge 250 files!” 320312 Software Engineering (P. Baumann) 2
More Chaos …. Software delivery problems: • “Which configuration does this customer have?” • “Did we deliver a consistent configuration?” • “Did the customer modify the code?” • “The customer skipped the previous two releases. What happens if we send him the new one?” …familiar to anyone who has worked in software development. 320312 Software Engineering (P. Baumann) 3
Definition Software Configuration Management (SCM) = the discipline of controlling the evolution of software systems SCM indispensable for large, long-lived software! 320312 Software Engineering (P. Baumann) 4
Three Classic CM Problems Configuration management must address at least the following key problems: • The double maintenance problem Prevent the occurrence of multiple copies of the same file that must be independently updated. • The shared data problem Allow two or more developers with access to the same file/data. • The simultaneous update problem Prevent file clobbering from two developers updating the same file at the same time. 320312 Software Engineering (P. Baumann) 5
Versions Data base (vault) Workspace (sandbox) Fix.1 checkout 1.1 1.2 1.3 2.1 2.2 2.3 2.3 2.3 checkin Par.1 Par.2 Revision-of Variant-of Change cycle: 1. checkout 2. modify copy in workspace 3. checkin 320312 Software Engineering (P. Baumann) 6
Versions: Terminology Version ::= revision | variant Revision: A software object that was created by modifying an existing one Variant: Two software objects sharing an important property, differing in others • user interface, platform, algorithms, data structures, user groups, … 320312 Software Engineering (P. Baumann) 7
Using Deltas to Reduce Version Space Data base (vault) Workspace (sandbox) Fix.1 checkout 2.2 2.3 2.3 2.3 1.1 1.2 1.3 2.1 2.2 checkin Par.1 Par.2 A delta is a difference between two revisions. Can be computed in forward or backward direction on checkin. Used to regenerate one revision from another. 320312 Software Engineering (P. Baumann) 8
Merging of Versions line based produces too many false conflicts Full semantic merging not practical Structural merges (smart merges) • Ex: developer A changes identifiers, developer B changes code using the old identifiers. Now what? • research stage 320312 Software Engineering (P. Baumann) 9
Version Selection For Configuration Compiler Lexical Analysis Back End Semantic Analysis Syntactic Analysis Optimization Code Generation System Model Version Groups Baseline 320312 Software Engineering (P. Baumann) 10
Configuration: Terminology Release: a version that has been made available to user / client Configuration: combination of components into a system according to case-specific criteria Baseline: a static reference point for any configurable items in your project • does not imply that baseline is "perfect". It is only stating, in an example of software development, that the current version of the code is locked down so it can be verified and validated (tested) • Beware: used with various connotations; see http://projectmanagement.ittoolbox.com/documents/popular-q-and-a/meaning-of-baseline-in- the-software-project-1480 for a discussion 320312 Software Engineering (P. Baumann) 12
Configuration Models Three major models: Composition Model • Configuration = set of software objects -- module oriented aspect Change Set Model • Configuration = bundle of changes -- dynamic aspect Long Transaction Model Configuration = all changes are isolated into transactions -- collaborative aspect • Common understanding: configuration = selection (according to some individual criteria) of components from repository which together make up a release 320312 Software Engineering (P. Baumann) 13
Ex: Furniture Configuration Available product parts are combined into the variety of products offered Sample configuration: Instructions: Attach Legs L1 • Configuration name with Bolts B1 Table top TT1 to TT1; ... "Table MySweetHome" • Enumeration of elements, Legs L1..L4 plus their pertaining versions Bolts B1..B4 (components, user documentation, …) • Process description: how to generate & package • Responsible employee • … 320312 Software Engineering (P. Baumann) 14
Configurations in rasdaman Operating systems: • Linux, Solaris, HP-UX, DEC Tru64, AIX, ... Compilers • (gcc 2.95) / gcc 3.3 / gcc 4 / ... Database systems: • Oracle, DB2, Informix, PostgreSQL, MySQL With or without debug (internal test version) Release timeline: ..., 3.6, 5.0, 5.1pre, 5.1, 5.2, 6.0, 6.1; 7.0; 8.0, 8.1, 8.5, 9.0 320312 Software Engineering (P. Baumann) 15
Rule-Based Configuration Building (sample roles) [ versions | configurations ] 1. Baseline (aka "default"): 4. Reconfiguration: no versions, no selection needed select according to … + variants by attribute (e.g. platform=Unix) 2. Developer: 5. Time machine: select all version checked out by me, select according to … + the newest revision on main branch for others. + ignore everything after a cutoff date. 3. Cautious Developer: 6. New Release: select last baseline select according to … + the newest, stable versions that are + all version checked out by me associated with a given configuration of + all versions checked in by me change requests 320312 Software Engineering (P. Baumann) 16
Tools: svn & friends SVN (subversion) CVS RCS [Tichy, 80s] SCCS • GUI frontends: RapidSVN, TortoiseSVN Some svn commands: • svn import http://yourhost/svn/repos myproject myproject • Don't forget the last argument, or else all of the files in myproject will be dumped into the main SVN repository directory... at the top of the hierarchy • svn checkout http://yourhost/svn/repos/myproject/trunk -d myproject • svn status myfile.cc • svn update myfile.cc • svn diff myfile.cc • svn commit myfile.cc diff, tkdiff 320312 Software Engineering (P. Baumann) 17
Tools: make "make": controls generation of derivatives from their prerequisites Configuration rule base: (i) builtin, (ii) Makefile, makefile Rule format: target: prerequisites how-to-generate Macro: aka variable • SRC = myclass1.cc myclass2.cc • gcc – o $(OBJECTS) ... $@ Full name of current target $? current dependencies out-of-date $< source file of current dependency 320312 Software Engineering (P. Baumann) 18
Multi-Step Generation Makefile can contain any number of rules Advantage: update only when needed server : server.o socket.o database.o /home/xyz1234/Messages/libmsg.a cc -o server server.o socket.o database.o \ /home/xyz1234/Messages/libmsg.a server.o : server.c continuation cc -c server.c line socket.o : socket.c cc -c socket.c database.o : database.c cc -c database.c 320312 Software Engineering (P. Baumann) 19
How Make Sees Your Project 320312 Software Engineering (P. Baumann) 20
Summary Configuration Management for controlling change through life cycle • Version/revision/variant, release/configuration • svn, git • diff Rule-based code generation • make • also used for configuration 320312 Software Engineering (P. Baumann) 21
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